Teeth with dental decays such as cavities are generally restored by removing the decayed area and applying a restorative thereon. Traditionally, amalgam material has been used for filling and repairing teeth. Because the amalgam material tends to harden as it is being worked, and its thick, lumpy consistency necessitates using specialized tools for pushing the material into corners and crevices to facilitate adaptation to the tooth, its use is inconvenient and causes great discomfort to the patient. Moreover the retention of an amalgam restorative in a tooth is by bulk, for repairing a small decayed area, often an amount of healthy tooth structure many times the decayed area has to be removed to provide room to receive the amalgam material.
The concern of the presence of mercury in amalgam material has led to the introduction of other restoratives that do not contain mercury. For example, "Universal Paste" composites, such as P-50 and Z-100 sold by 3M Company, have been used for restoring teeth. Examples of other composite materials that can be used for repairing teeth include the compositions disclosed in U.S. Pat. No. 4,553,940 (Koblritz, et al) and U.S. Pat. No. 5,228,907 (Eppinger, et al).
Generally, composite materials for repairing teeth are thick and sticky, making them difficult to work with and highly technical skill is required of the operator to properly place such materials in teeth for restoration purposes. Universal paste type composites are generally used by trowelling an amount of the paste into position in a hollow (or void or cavity), tamping the paste down to improve contact with the surface of the cavity, carving the excessive paste into a rough outline of the desired shape, and polishing the cured composite to a desired shape and smoothness.
Because a composite material, similar to amalgam material, is generally applied as a lump in the prepared location in a tooth, voids and porosities are often incorporated into the material during placement because of the difficulty in manipulating the material into corners and crevices in the tooth. Furthermore, if a composite material is light curable, because of the thickness of the composite material applied, incomplete polymerization often results.
Another kind of restorative material that does not contain mercury is a film-forming composition that is generally used as a sealant, glaze, or adhesive. Typically, such a film-forming dental composition contains resins with little or no filler materials. Such film-forming dental compositions are typically used for sealing the tooth against cracks adjacent to fillings. Such compositions generally have low viscosity and can be applied to the tooth by using a brush. An example of a sealant is disclosed in U.S. Pat. No. 4,001,483 (Lee, Jr., et al.). Such a composition is generally applied as a thin coating and when cured, forms a sealing coat on the tooth. Yet another kind of coating composite is used for masking stains and discolorations. For example, U.S. Pat. No. 4,150,485 (Lee, Jr., et al) discloses a brushed-on dental restorative coating composition used for covering surface imperfections. This composition has a higher viscosity than conventional sealants. Such film-forming and coating compositions have not been applied in restoration of tooth decays such as filling cavities.